Authenticating / Refreshing Google API access token and avoiding a "file in use" exception?

This is how I authenticate for using the Google API:

Private Function DoAuthentication(ByRef rStrToken As String, ByRef rParameters As OAuth2Parameters) As Boolean
    Dim credential As UserCredential
    Dim Secrets = New ClientSecrets() With {
        .ClientId = m_strClientID,
        .ClientSecret = m_strClientSecret
    }

    m_Scopes.Add(CalendarService.Scope.Calendar)

    Try
        credential = GoogleWebAuthorizationBroker.AuthorizeAsync(Secrets, m_Scopes,
                                                                 "user", CancellationToken.None,
                                                                 New FileDataStore("XXXXX.Application")).Result()

        If credential.Token.IsExpired(Google.Apis.Util.SystemClock.Default) Then
            credential.RefreshTokenAsync(CancellationToken.None)
        End If


        ' Create the calendar service using an initializer instance
        Dim initializer As New BaseClientService.Initializer() With {
            .HttpClientInitializer = credential,
            .ApplicationName = "xxx"
        }
        m_Service = New CalendarService(initializer)

        rStrToken = credential.Token.AccessToken.ToString()
        rParameters.AccessToken = credential.Token.AccessToken
        rParameters.RefreshToken = credential.Token.RefreshToken
    Catch ex As Exception
        ' We encountered some kind of problem, perhaps they have not yet authenticated?
        ' Can we isolate that as the exception?
        m_logger.Error(ex, "DoAuthentication")

        Return False
    End Try

    Return True
End Function

And then in my Main:

Dim parameters As New OAuth2Parameters
If (DoAuthentication(strToken, parameters)) Then
    iResult = RESULT_SUCCESS_OAUTH
Else
    Return RESULT_FAILED_OAUTH
End If

It then continues. The problem is that sometimes, even though the "authenticate" succeeds so that it starts to run the rest of the code. that I then get an exception:

2020-11-30 18:47:03.6762|ERROR|GoogleAuthandSync.Program|AddEventsToCalendarXML|System.IO.IOException: The process cannot access the file 'C:\Users\USERNAME\AppData\Roaming\XXXXX.Application\Google.Apis.Auth.OAuth2.Responses.TokenResponse-user' because it is being used by another process.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)

How can I authenticate / refresh the token and make sure we are ready to proceed so that this exception stops? It doesn't always happen.

(I renamed the token file for security in the code / error text above).

Should I be using the Await keyword?

If credential.Token.IsExpired(Google.Apis.Util.SystemClock.Default) Then
    Await credential.RefreshTokenAsync(CancellationToken.None)
End If

Would that make a difference? I notice that in this sample code they use await.